1. Field of the Invention
The present invention generally relates to hinge mechanisms and, more particularly, to a hinge mechanism for hinging together housings of a foldable electronic device, such as a mobile phone or a PDA (Personal Digital Assistant).
2. Discussion of the Related Art
Many mobile phones and other portable electronic devices have two housings rotatably joined by a type of hinge that allows the housings to fold upon one another. Many such foldable mobile phones have most of the electronics in one housing, called the main housing, and fewer electronics in the other housing, called the cover. Other such foldable mobile phones have all the electronics in the main housing, with the cover serving only to cover a keypad and a display of the main housing. The main housing and the cover are connected together by a hinge mechanism. A typical hinge mechanism for foldable mobile phones and other portable electronic devices incorporate a torsion spring to achieve the rotation between the main housing and the cover in order to help the device to selectably remain closed or open.
One such kind of hinge mechanism is disclosed in U.S. Pat. No. 6,493,542, the contents of which are hereby incorporated by reference thereto. Referring to FIG. 1 of the present application, the hinge mechanism includes a sleeve 91, a torsion spring 92, and a main shaft 93. The sleeve 91 is substantially a hollow cylinder, with an open end and an opposite closed end. Disposed proximate the opposite closed end is an end portion 912 for latching with a cover section (not shown) of a foldable mobile phone (also not illustrated). Additionally, near the opposite closed end but opposing the end portion 912 is defined a blind receiving hole 914, with inner threads. A given finger 922, 924 extends from the two ends of the torsion spring 92, respectively. The main shaft 93 has a fixing portion 932 at one end thereof and a flange 934 at another opposite end. The fixing portion 932 has outer threads defined thereon.
In assembly, the torsion spring 92 is received in the sleeve 91. The finger 924 is engaged with a body section (not shown) of the foldable mobile phone. The main shaft 93 is inserted into the sleeve 91, and the fixing portion 932 is mounted into the blind receiving hole 914 of the sleeve 91. The hinge mechanism thus is completely assembled. The duly assembled hinge mechanism is then received in the body section of the foldable mobile phone. The end portion 912 is engaged with a cover section (not shown), and the finger 924 is operative with the body section. When the cover section is closed, the torsion spring 92 has a predetermined torsion. At the same time, the cover section is mated through a locking mechanism (not shown), such as a magnet. The magnetic force can make the cover section close to the body section.
When in use, the locking mechanism is released, and the cover section is opened via the torsion of the spring 92. The structure of the hinge mechanism is simple, and the operation is convenient. However, the torsion force of the whole hinge mechanism suffers from the end portion 912 of the sleeve 91. The end portion 912 is small and thus requires a higher strength. Furthermore, the impact force burdens the body section and the cover section. The body section and the cover section, as such, are easily worn, thereby shortening the working lifetime of the foldable mobile phone. Moreover, the body section must be specially constructed in order to permit engagement thereof with the finger 924. Therefore, the hinge mechanism has a poor exchangeability (i.e., not readily interchangeable), which could increase the cost of the mobile phones employing such a hinge mechanism.
What is needed, therefore, is a new hinge mechanism that overcomes the above-described problems.